Electrically steerable horn antenna system



Dec. 6, 1960 B. e. HAGAMAN ELECTRICALLY STEERABLE HORN ANTENNA SYSTEMFil'ed Sept. 25, 1957 2 Sheets-Sheet 2 enm WZQQNTI 29.2810 n5 M GZQ ..N\

90 N/ 073/;1 NOLLV/OVH NI 073/4! NOLLV/OVZ INVENTOR I ATToibiE Y UnitedStates Patent ELECT RICALLY STEERABLE HORN ANTENNA SYSTEM Boynton G.Hagaman, Alexandria, Va., assignor to Antenna Systems, Inc., Washington,D.C., a corporation of Delaware Filed Sept. 25, 1957, Ser. No. 686,213

9 Claims. (Cl. 343-100) The present invention relates to an electricallysteerable horn antenna system and particularly to a feed system for ahorn antenna which provides electrical steering of the major radiationlobe with respect to the major horn axrs.

An object of the present invention is to provide a horn antenna systemin which the directivlty is controllable over both the E and H planes ofthe horn and in which the major beam dimensions are not materiallyaltered during steering.

Another object of the invention is to steer the radiation of the hornantenna in either, or both, the E and H planes simply by electricaladjustment of components in the horn feed system, Without the necessityof moving the horn or other mechanical elements.

Another object of the invention is to provide electrical steering of theradiation of a horn antenna mounted several wave lengths above the earthin such a manner that over a range of frequencies, the usual variationin elevation or departure angle caused by the earths reflections iseliminated.

According to the invention, the radiation of the horn antenna is steeredor shifted by feeding the horn with a plurality of probes which arespaced apart in the direction of the E vector or the H vector, or both,and the phases of the energy of the several probes are adjusted relativeone to the other so as to obtain a desired direction of radiation fromthe horn.

The invention will be fully understood and the above other objects andadvantages of the invention will become apparent from the followingdescription and the drawings in which:

Fig. 1 is a schematic view of one embodiment of the invention;

Fig. 2 shows radiation patterns obtained with the arrangementillustrated in Fig. 1;

Fig. 3 shows another embodiment of the invention for steering the beamin the H plane;

Fig. 4 shows a radiation pattern obtained with the arrangement shown inFig. 3; and

Fig. 5 shows another embodiment of the invention for steering theradiation in both the E and H planes.

Referring to Fig. 1, there is shown a pyramidal horn having a wave guidesection 11. The wave guide 11 is provided with a bisecting metallicpartition 12, lying in the H plane, which is here the vertical plane.Wave guide section 11 is closed at one end by a metallic wall 14. A pairof probes 15 and 16 extend through opposite side walls 17 and 18. Probe15 is connected to a generator or a receiver 19 by a radio frequencytransmission circuit which may consist of transmission lines 20 and animpedance matching and/ or attenuation pad 21. Probe 16 is similarlyconnected by transmission line 22 to a pad 23 and then through avariable phasing network 25 to the generator or receiver. Probes 15 and16 are arranged and have a length such that wave guide 11 is excited ina TB 10 mode. Simple aligned probes may be used where 2,963,701 PatentedDec. 6, 1960 ice band-width requirements are moderate, however, thesystem may be made capable of handling broad frequency hands by any ofthe usual methods.

Phasing network 25 has a nominal phase delay of this being necessarysince the probes are fed from opposite ends. If the phasing network 25is adjusted to provide additional phase delay of the energy fed to probe16, the radiation from the horn will be steered in the direction towardprobe 16. Fig. 2 illustrates the directivlty control obtained withprogressive increments of phase delay in network 25. Each curve showsthe radiation pattern of the beam for a particular setting of phasingnetwork 25. The amount of steering or turning of the beam in Fig. 2, isapproximately 10, as represented by the angular shift to the left of thepeaks of the curves from curve 26 to curve 27. Similar shifting of theradiation pattern in the opposite direction is obtained by relativedelay of the energy fed to probe 15. The steering represented in Fig. 2,is in the E plane or the azimuthal direction.

Fig. 3 shows another embodiment of the invention in which a pyramidalhorn 30 is connected to a wave guide section 31. A pair of probes 32 and33 are located at approximately one third the distance h from the topand the bottom of the wave guide. The distance h is to be at least equalto one wave length at the operating frequency. Probe 32 is connected bya transmission line or equivalent radio frequency path 34 to a generatoror receiver and probe 33 is similarly connected through a transmissionline 35 and an adjustable phasing network 36 to a generator or receiver37. It will be understood that suitable radio frequency pads may beincluded in transmission lines 34 and 35 as indicated in Fig. 1.

Fig. 4 shows the steering of the radiation beam in the vertical or the Hdirection which is obtained with the arrangement illustrated in Fig. 3.Curve 40 shows the radiation pattern of the horn antenna when phasingnetwork 36 is adjusted to zero delay or, in other words, when probes 32and 33 are energized in the same phase. Curves 41, 42 and 43 show theprogressive shifting of the radiation pattern as network 36 is adjustedto increase the phase delay. Similar shifting of the radiation patternin the opposite direction is obtained by a relative delay of the energyfed to probe 32.

Horn antenna 30 may be placed several wave lengths above the earth withits axis horizontal or at a slight elevation. Phasing network 36 maythen be used to vary the phase delay with frequency so that the usualvariation in departure angle or elevation angle caused by the earthsreflections is eliminated over a wide range of frequencies.

The systems shown in Figs. 1 and 3, may be combined so that theradiation of the horn can be steered to a considerable extent in anydirection. Fig. 5 illustrates such an arrangement. The horn 50 isprovided with a wave guide 51 which is partitioned by a median metallicwall 52 extending in the vertical or H direction. A pair of probes 53and 5-4 are positioned similarly to probe 32 and 33 of Fig. 3 andconnected through suitable transmission lines 55 and 56 and pads 57 and58. Pad 57 is connected through an adjustable phase shift network 59,the input of which is connected to a generator or receiver 61 throughanother phase shifting network 60. Probes 63 and 64 are similarlyconnected through pads 65 and 66 and an adjustable phase shiftingnetwork 67 to the generator or receiver. It will be evident from thediscussion given above, that phasing networks 59, 60 and 67 are capableof shifting the radiation beam in either the H plane or the E plane, orboth.

I have shown and described several embodiments of my invention in orderto illustrate the principles thereof. Many variations of the structuresherein shown and described will be apparent to those familiar with thisart,

therefore my invention is not to be construed as limited except asdefined in the following claims.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

1. An electrically steerable horn antenna system comprising arectangular fiaring horn radiator, a rectangular wave guide connected tothe small end of the born, a pair of antennas in said wave guideextending in the direction of the electric vector in the wave guide andarranged to excite said wave guide in a TE- mode, said antennas beingspaced apart in a direction perpendicular to the axis of the wave guide,radio frequency apparatus, radio frequency transmission means connectingsaid apparatus to said antennas, and variable means in said transmissionmeans for changing the direction of the major lobe of the radiationpattern, said variable means comprising phase shifting means for varyingthe relative phase delay between said respective antennas and the radiofrequency apparatus.

2. A system according to claim 1, wherein said antennas are linearradiators extending through opposite walls of the wave guide.

3. A system according to claim 2, wherein said wave guide includes abisecting metallic partition therein extending in the H plane.

4. A system according to claim 1, wherein said antennas are linearradiators extending through the same side wall of the wave guide and arearranged in the same H plane.

5. A system according to claim 4, wherein said wave guide has a height hin the H plane and said antennas are spaced respectively /3 h from thetop and the bottom walls of the wave guide.

6. A system according to claim 5, wherein said wave guide includes abisecting metallic partition extending in the H plane, a second pair ofantennas extending into the wave guide through the opposite side wallthereof, each of said second antennas being positioned opposite one ofthe antennas of the first pair, phase adjusting means connected betweensaid radio apparatus and the second pair of antennas for cooperatingwith said first mentioned phase shifting means for steering theradiation pattern in either, or both, the E and the H planes.

7. An electrically steerable horn antenna system comprising a pyramidalhorn radiator, a rectangular wave guide connected to the small end ofthe horn, a metallic partition in an H plane bisecting said wave guide,a pair of linear probes in said wave guide extending from opposite sidewalls thereof in the same E plane, radio frequency apparatus, radiofrequency transmission means connecting said apparatus to said probes,and variable means in said transmission means for steering the directionof the major lobe of the radiation pattern in the plane of said probes,said variable means comprising an adjustable delay network for varyingthe relative phase delay between said respective probes and the radiofrequency apparatus.

8. An electrically steerable horn antenna system comprising a pyramidalhorn radiator, a rectangular wave guide connected to the small end ofthe horn, a pair of linear probes in said wave guide extendingperpendicularly from one side wall thereof in the same direction in an Hplane, radio frequency apparatus, radio frequency transmission meansconnecting said apparatus to said probes, and adjustable means in saidtransmission means for steering the direction of the major lobe of theradiation pattern in the plane of said probes, said adjustable meanscomprising phase shifting means for varying the relative phase delaybetween said respective probes and the radio frequency apparatus.

9. The method of operating a horn antenna so as to prevent variations inthe departure angle of the radiation caused by the earths reflections,comprising the step of mounting the antenna several wave lengths abovethe earths surface for radiation at said angle and exciting a wave guideconnected to the horn in a TB 10 mode and adjusting the relative phasedelay in a pair of transmis sion paths connected between radio frequencyapparatus and a pair of antenna probes extending into the wave guide inaccordance with variations of the frequency of the radio frequencyenergy so that the departure angle remains nearly constant.

References Cited in the file of this patent UNITED STATES PATENTS2,245,660 Feldman June 17, 1941 2,464,276 Varian Mar. 15, 1949 2,556,094Lindenblad June 5, 1951 2,810,908 Crawford Oct. 22, 1957

